Isolation and Culture of FMDV Strains

BHK-21 cells were grown in Dulbecco’s modified Eagle’s medium (DMEM, Gibco) supplemented with 10% fetal bovine serum (FBS, Hyclone). Goat fibroblasts were kindly provided by Prof. Baohua Ma (Northwest Agriculture & Forestry University) and cultured in DMEM/F12 nutrient mixture (Gibco) (containing 1.5 g/L sodium bicarbonate) supplemented with 10% FBS. All cell lines were incubated at 37°C with 5% CO₂. Kunming White suckling mice, 2–3 days old and weighing 3–4 g, were purchased from Lanzhou Institute of Biological Products. Five FMDV isolates, O/Tibet/China/1/99 [PanAsia-1 strain of ME-SA (Middle East-South Asia) topotype, AF506822], O/HN/CHA/93 (vaccine strain of Cathay topotype) [67 (link)], O/CHN/Mya98/33-P [Mya98 strain of SEA (South-East Asia) topotype, JQ973889], and AF72 (vaccine strain of Asia topotype) [68 (link)], Asia 1/Jiangsu/China/2005 (vaccine strain of SEA topotype, EF149009), were preserved and provided by OIE/National Foot-and-Mouth Disease Reference Laboratory of China.